Efficient Electrooxidation of 5-Hydroxymethylfurfural Using Co-Doped Ni₃ S₂ Catalyst: Promising for H₂ Production...

Replacing oxygen evolution reaction (OER) by electrooxidations of organic compounds has been considered as a promising approach to enhance the energy conversion efficiency of the electrolytic water splitting proces. Developing efficient electrocatalysts with low potentials and high current densities is crucial for the large-scale productions of H₂ and other value-added chemicals. Herein, non-noble metal electrocatalysts Co-doped Ni₃ S₂ self-supported on a Ni foam (NF) substrate are prepared and used as catalysts for 5-hydroxymethylfurfural (HMF) oxidation reaction (HMFOR) under alkaline aqueous conditions. For HMFOR, the Co_0.4 NiS@NF electode achieves an extremely low onset potential of 0.9 V versus reversible hydrogen electrode (RHE) and records a large current density of 497 mA cm^-2 at 1.45 V versus RHE for HMFOR. During the HMFOR-assisted H₂ production, the yield rates of 2,5-furandicarboxylic acid (FDCA) and H₂ in a 10 mL electrolyte containing 10 × 10^-3 M HMF are 330.4 µmol cm^-2 h^-1 and 1000 µmol cm^-2 h^-1 , respectively. The Co_0.4 NiS@NF electrocatalyst displays a good cycling durability toward HMFOR and can be used for the electrooxidation of other biomass-derived chemicals. The findings present a facile route based on heteroatom doping to fabricate high-performance catalyses that can facilitate the industrial-level H₂ production by coupling the conventional HER cathodic processes with HMFOR.